Recently, along with further reduction in size of electric and electronic components such as a connector, a relay and a switch, the density of a current which flows in a contact member and a sliding member incorporated therein has been increasingly increased, and there has been an increasing demand for a material with better conductivity than in the related art. In particular, vehicle electronic components are required to reliably endure a higher temperature and vibration environment for a long period of time and desired to have excellent stress relaxation properties.
As materials capable of responding to such requirements, a Cu—Zr-based alloy can have a high conductivity of more than 80% IACS and has good heat resistance and excellent stress relaxation properties. However, there is a problem of retaining bending workability while satisfactory strength is secured, and excellent bending elastic properties are also required.
As a Cu—Zr-based copper alloy to solve such problems, in PTL 1, a copper alloy is disclosed which allows the strength and elongation to be balanced at a high level, contains, in terms of a weight ratio, 0.005% to 0.5% of Zr, and 0.2 ppm to 400 ppm of B, and has a layered structure composed in such a manner that crystal grain layers made of plural flat crystal grains continuous in a plane direction are laminated in a thickness direction. The thickness of the crystal grain layer is in a range of 20 nm to 550 nm, a peak value P in a histogram of the thickness of the crystal grain layers in the layered structure is in a range of 50 nm to 300 nm, and is also present at a frequency of equal to or more than 22% of the total frequency, and a half-value width L thereof is equal to or less than 200 nm.
In PTL 2, a copper alloy is disclosed which allows the strength and elongation to be balanced at a high level, contains, in terms of a weight ratio, 0.005% to 0.5% of Zr, and 0.001% to 0.3% of Co, and has a layered structure composed in such a manner that crystal grain layers made of plural flat crystal grains continuous in a plane direction are laminated in a thickness direction. The thickness of the crystal grain layer is in a range of 5 nm to 550 nm, a peak value P in a histogram of the thickness of the crystal grain layers in the layered structure is in a range of 50 nm to 300 nm, and is also present at a frequency of equal to or more than 28% of the total frequency, and a half-value width L thereof is equal to or less than 180 nm.
In PTL 3, a copper alloy material for electric and electronic components is disclosed which has high mechanical strength and bending formability and is obtained by rolling a copper alloy containing zirconium (Zr) of equal to or more than 0.01% by mass and equal to or less than 0.5% by mass, and a remainder including Copper (Cu) and unavoidable impurities. The orientation distribution density of Brass orientation in a texture of the copper alloy material for electric and electronic components is equal to or less than 20, and the sum of the respective orientation distribution densities of Brass orientation, S orientation and Copper orientation is equal to or more than 10 and equal to or less than 50.